Wet bottom boiler floor or the like



Nov. 25, 1969 K, FREVEL 3,479,993

WET BOTTOM BOILER FLOOR OR THE LIKE Filed June 3, 1968 2 Sheets-Sheet 1 INVENTOR. Lao/o K. Fe n/e/ Nov. 25, 1969 K, FREVEL 3,479,993

WET BOTTOM BOILER FLOOR OR THE LIKE Filed June 5, 1968 v 2 Sheets-Sheek'I 2 INVENTOR. ao/o K. Ffeve/ United States Patent O U.S. Cl. 122-235 8 Claims ABSTRACT OF THE DISCLOSURE In wet bottom boilers or the like the boiler tubes on or adjacent to the boiler floor are formed into a unitary structure and are surrounded on their top side with dense, high melting point particulated material such as monazite sand, for example.

Lateral movement of the particulated material is restricted by a series of so-called dams extending transverse to the boiler tubes and by an array of protective elements (rods or plates) disposed above the dams.

' Such a structure prevents localized overheating, weakening, and eventual rupturing of the boiler tubes by preventing molten iron, iron sulfide or other molten, heavy substances present in molten slag from contacting the boiler tubes.

Background of the invention This invention relates to apparatus wherein metal tubes are contacted by fused, iiowable heated materials, and particularly to sof-called Wet-bottom boilers.

In so-called wet-bottom boilers the tubes along the floor of the boiler are contacted by molten slag which is withdrawn from the floor at one or more points.

It has been found that the iron-aluminum silicate part of the slag in the boiler also contains heavier substances such as molten iron and iron fulde which tend to sink to the bottom of the molten slag and contact the boiler tubes. It is believed that the puddles of highly active molten iron and heavy iron sulfide tend to cause localized overheating of boiler tubes which eventually weaken boiler tubes to the point where rupturing of the tubes occurs.

Accordingly, a principal object of this invention is to provide improved boiler apparatus having means for preventing molten slag rom contacting boiler tubes.

Another object of this invention is to provide an irnproved, safer wet bottom boiler.

In accordance with this invention an array of boiler tubes on the floor of a so-called wet bottom boiler are formed into a unitary boiler fioor structure and covered with a dense particulated high melting point material. Movement of the particulated material is restricted by dam-like elements which are disposed transversely with respect to the tubes and by an array of overhead elements disposed just above the tubes. In some instances part of the particulated material extends slightly above the overhead elements.

A layer of solidified slag usually forms above the overhead elements, with the molten slag being above that layer. Thus, the above-mentioned assembly isolates the boiler tubes on the floor of the boiler from direct physical contact with molten slag.

The invention, as well as additional objects and advantages thereof, will best be understood when the following detailed description is read in connection with the accompanying drawings, in which:

FIG. 1 is a simplified fragmentary diagrammatical view of a wet bottom boiler;

FIG. 2 is a transverse sectional view of a boiler tube assembly in accordance with this invention;

3,479,993 Patented Nov. 25, 1969 FIG. 3 is a fragmentary top view of the boiler tube assembly of FIG. 2;

FIG. 4 is a transverse sectional view of an alternative boler tube assembly in accordance with this invention; an

FIG. 5 is a sectional view, taken along the line 5 5 of FIG. 4.

Referring to the drawing, and particularly to FIG. l, there is shown a representation of a boiler tube assembly composed of arrays 10, 12 of vertically disposed boiler tubes, a header 14, and an array of tubes 16 along the floor of a boiler. The array 16 slopes downwardly toward a slag discharge tube 18 disposed usually in the central section of the floor of the furnace.

Usually, when an array of boiler tubes is installed, a layer of chromite ore is disposed above yand about the boiler tubes to isolate the tubes from molten slag. However, during operation of the boiler, the chrome ore appears to be leached away by the molten slag at a fairly rapid rate. Further, the chromite ore is apparently wet by molten iron and/or iron sulfide, so those materials may flow through the ore and contact the boiler tubes.

Referring now to FIGS. 2 and 3, there is shown an array of boiler tubes 20a, 20b, 20c joined to each other by strips 22, 24 for example, to form a unitary boiler floor. An array of long studs 26 and short studs 28 extend upwardly from the strips 22, 24 (and other strips not numbered) above the top of the tubes 20a, etc.

An larray of strip-like dam elements 34, having their underside contoured to fit around the part of the boiler tubes which extend above the strips 22, 24, are disposed transversely to the boiler tubes, usually lying between spaced apart studs 26, 28. Other means for fastening the dam elements in position may be used, however, provided the means used doesnt adversely affect the boiler tubes.

An array of fiat metal plates 30 are disposed over the dam elements 34 and short studs or other spacer means 28, the plates 30 being held in position by the long studs 26 which extend through bores 27 in the plates 30.

The space between the plates 30 and the actual floor of the boiler is filled (or at least substantially filled initially) with a dense, particulated high melting point material such as monazite sand 32, for example.

FIGS. 4 and 5 illustrate an alternative embodiment of the invention in which elongated vertical upwardly extending strips 48 are tacked to the strips 44, 46, for example, which join together the tubes 36, 38, 40, for example, of the array of boiler tubes to form a unitary floor structure.

An array of rods 50 are tacked to the upper part of the vertical strips, such as 48, 50, at intervals, the bars being transverse to the length of the tubes 36, 38, 40, parallel with each other, and spaced from each other by a distance which is a minor fraction of the rod diameter.

The open space between the rods and the strips 44, 46 (for example) and up to or somewhat beyond the top of the rods 50 is substantially filled with dense, particulated, high melting point materials, such as Monazite sand, for example.

It is realized that the monazite sand will shift, and the actual degree of filling the entire space described above depends on the slope of the boiler bottom, which is supported below by beams 42.

In operation, in the embodiment of FIGS. 3 and 4, the dam elements 34 serve the useful function of helping to prevent excessive ow or movement of the particulated material 34 as well as provide support for the plates 30.

The plates 30 prevent the excessive moving of the particulated material 32 by moving slag in the boiler, conduct heat from the slag to the boiler floor assembly, and act as sacrificial material with respect to molten iron, iron 3 sulde or the like which passes through the slag bed in the boiler.

Usually a layer of frozen slag occurs just above the plates 30, with the molten slag lying above that layer.

Because the plates merely lit over the studs 26 and rest 0n the dam elements 34, short studs 28, and the particulated material 32, any damaged plates may easily be replaced.

In connection with the operation of the embodiment of FIGS. 4 and 5, the particulated material is usually added While the array of rods is incomplete, the material 52 being poured through the spaces Where missing rods will later be inserted and tacked in place at intervals, but tacked so as to permit expansion and contraction of the rods. The closely spaced rods serve the function of both the darn elements and plates of the embodiment of FIGS. 3 and 4.

The upwardly extending strips (48, 50) extend above the top of the tubes 36, 38, 40, for example, about 1/2 in'ch. The rods 50, made of iron, are about 1 inch to 1% iiich in diameter, and are spaced apart, typically, about 1A; inch. The rods hold the sand, provide a means for transferring heat, and perform a sacrificial function if molten iron or iron sulfide from the molten slag layer 56 passes through the layer 54 and contacts the rods 50.

The particulated material 52 extends about 1/2 inch above the rods 50, as initially installed.

Monazite sand, having a density of about 52 grams per cubic centimeter, should be installed as dry sand on a Warm boiler floor.

The plates 30 of FIGS. 2 and 3 are usually 1A inch thick steel plate. Although a plurality of plates 30 are illustrated, a single plate having suitable venting perforations may be used.

Particulated zirkite ore is an example of a material which may be substituted for monazite sand.

What is claimed is:

1. A heat exchange assembly wherein heat is transferred from a hot mass which may contain localized masses of hot corrosive material to an array of tubes containing a circulating lluid, comprising an array of tubes joined to each other by sheet means to form a unitary structure, metal means extending upwardly beyond said tubes from said sheet means for supporting a shielding structure overhead with respect to said tubes, said shielding structure comprising an array of metal elements carried on said metal means, said array including means for venting gases therethrough, and particulated dense high melting material, said material being disposed at least between said tubes and sheet means and said shielding structure.

2. An assembly in accordance with claim 1, wherein said support structure is an array of spaced apart plates.

3. An assembly in accordance with claim 1, wherein said support structure is an array of substantially parallel metal bars disposed in predetermined spaced relationship with one another, said spaced relationship being such that said bars are separated by a length which is a minor fraction of the distance through each bar as measured transversely to said array.

4. An assembly in accordance with claim 1, wherein an array of dam elements is disposed transversely across said tubes, extending from at least near to said tubes and sheet means to above said tubes.

5. An assembly in accordance with claim 4, wherein said supporting structure is carried on Said dam elements and on studs extending upwardly from said sheet means.

6. An assembly in accordance with claim 1, wherein said particulated material is monazite sand.

7. An assembly in accordance with claim 3, wherein said particulated material extends above said bars.

8. An assembly in accordance with claim 3, wherein said particulated material is comprised of zirkite ore.

References Cited UNITED STATES PATENTS 1,825,933 10/1931 Lucke 122-235 2,025,266 12/ 1935 Broz 122-6 2,148,484 2/ 1939 Lucke 122-235 KENNETH W. SPRAGUE, Primary Examiner 

